Colitis X

Description

Colitis X (so-called due to its unknown aetiology) is a peracute and highly fatal disease of horses. Is characterised by severe oedematous colitis, sudden watery diarrhoea and death within 24 hours. A number of possible underlying causes have been described, including drug or parasite hypersensitivity, salmonellosis and high-protein, low-cellulose diets. Recently a link has been demonstrated with the current human epidemic strain of C. difficile (ribotype 027/toxinotype III) clostridial enterocolitis. Stress (such as surgery or transport) has also been reported as a predisposing factor.

Signalment

Colitis X affects adult horses, usually between one and ten years old.

Clinical Signs

• Abdominal pain
• Acute onset watery to haemorrhagic diarrhoea
• Tachycardia (Heart rate often greater than 100bpm)
• Dehydration
• Signs relating to hypovolaemic or endotoxic shock, e.g. congested mucous membranes, prolonged capillary refill time, cold extremities.
• Dilated pupils
• Collapse
• Body temperature may vary from pyrexic to subnormal
• Bowel sounds may be absent

The clinical signs are similar to those described for other forms of acute- peracute colitis. Acute salmonellosis, grass sickness, acute small intestinal obstructions and intestinal thromboembolic infarctions are other differentials that must be considered.

Diagnosis and Pathology

The above examination findings combined with an increased plasma urea concentration (greater than 10 mmol/l), increased PCV (greater than 65 Diagnosis is often made post-mortem, where a hyperaemic or oedematous caecum and ventral colon may be seen with necrosis of the intestinal in the later stages of the disease. Numerous gram negative bacteria may be identified in the mucosa and submucosa. The intestinal tract may be filled with a foul smelling and watery content. Macroscopic and microscopic findings include signs of disseminated intravascular coagulation and large numbers of bacteria in the devitalized parts of the intestine.

Treatment

Treatment is often unsuccessful and horses may often require euthanasia. Treatment methods previously reported include aggressive fluid therapy with electrolyte replacement, antibiotics and analgesics. Pain is often severe in colitis x and potent analgesics such as flunixin meglumine are required. The administration of sodium benzyl penicillin may be beneficial as Clostridium spp are sensitive to this type of antibiotic.

Prognosis

The prognosis is usually poor, with a mortality rate approaching 90-100%. This may be lower for horses receiving intensive treatment.

References

• Glenn Songer, J., Trinh, H.T., Dial, S.M., Brazier, J.S., Glock, R.D. (2009) Equine colitis X associated with infection by Clostridium difficile NAP1/027 Journal of Veterinary Diagnostic Investigation 21:377–380

• Diakakis, N. (2008) Equine colitis X Journal of the Hellenic Veterinary Medical Society (Hellenic Veterinary Medical Society) 59:23–28(6)

• Schiefer H.B. (1981). Equine colitis "X", still an enigma? The Canadian Veterinary Journal. La Revue Vétérinaire Canadienne 22 (5):162–5

• White, N.A., Edwards, G.B. (1999) Handbook of Equine Colic Reed Educational and Professional Publishing Ltd

• Knottenbelt, D.C. A Handbook of Equine Medicine for Final Year Students University of Liverpool

• Rose, R.J. and Hodgson, D.R. Manual of Equine Practice Saunders Elsevier

• Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial